Highly saturated colors are often desirable in displayed video and images. Even unnaturally over saturated colors may often be seen as desirable by many people for video or image composition or viewing. Hence, user saturation adjustment knobs are commonly provided on display devices, even when the correct color display data is known via ancillary information.
Exceptions exist to the preference for over saturated color. For example, the color of human skin, also known as skin tone or “seashell pink”, is commonly objected to when over saturated. Other exceptions are natural objects for which a range of reference saturation overrides a general preference for over saturation. Therefore, a color adjustment setting that may be pleasing for the majority of video content is often different than an ideal desirable setting for human skin. Several studies have also shown that at least in some cultures (i.e., Japanese, Korean) there exists an “ideal” skin tone color that is perceived to be the most natural and pleasing color for skin.
Common approaches to adjusting skin tones involve segmenting out spatial areas of the pictures containing skin tone. Separate hue/saturation adjustments are then provided to control the segmented areas. However, the common approaches produce unacceptable results for video. Artifacts are introduced in the segmented areas when the pictures are viewed temporarily. As such, extra contour reduction steps are commonly implemented to reduce the artifacts created by the skin tone adjustment adding complexity. Furthermore, the common approaches do not adjust the color components of the video sequentially or operate in the native color space (i.e., CrCb). Hence, the common approaches cannot be implemented with linear operations or simple lookup tables resulting in expensive custom silicon.